The historic deal to cut teachers' workload comes into force this week more than two years after ministers and unions agreed to negotiate a solution to teacher overload.
More than 20 clerical and administrative tasks will be transferred from teachers to support staff as part of the agreement signed in January by the Government, employers and all the major unions except the National Union of Teachers.
PricewaterhouseCoopers have estimated that transferring administrative tasks to support staff could reduce teachers' workload by up to 10 per cent.
It is the most significant part of the first phase of the deal, which includes the introduction of a new clause in teachers' contracts promising them a reasonable work-life balance.
These measures will be followed next year by a limit on the amount of time teachers are expected to cover for absent colleagues of 38 hours per year.
By 2005, teachers will be entitled to guaranteed planning and preparation time equivalent to 10 per cent of their teaching hours.
The NUT has refused to sign the deal because it opposes the use of teaching assistants to take whole classes - a move the Government says is necessary to reduce the burden on teachers.
It will vote against the agreement at the TUC conference next week and instead calls for an extra pound;850 million for schools this year.
Implementation of the deal comes amid a growing row between the signatories over whether there is enough money to make it work.
The Secondary Heads Association warned that some schools are not ready to transfer tasks at the beginning of term - a situation that could lead to industrial action by the NUT and National Association of Schoolmasters Union of Women Teachers.
A TESSHA survey published last week suggested that 3,400 jobs have been lost in secondary schools alone as a result of the funding crisis.
Chris Keates, NASUWT deputy general secretary, accused SHA and The TES of being "doom and gloom merchants" and said they seemed "determined to ensure that teachers return to work demoralised and depressed".
Her reaction surprised other unions, as the NASUWT and SHA are widely seen as allies.
In a letter to The TES, David Hart, general secretary of the National Association of Head Teachers, accused the NASUWT of being "hell-bent on ramming through the agreement" and of showing "a lack of understanding of the situation on the ground".
John Bangs, NUT head of education, said: "Watching the signatories fall out with each other is no help to schools, which are losing staff as a result of the funding problems."
He accused the NASUWT of adopting a "Stalinist" approach to cutting workload after it told members that they should not continue with routine tasks - such as displaying children's work - even if they enjoyed doing them and did not want to stop.
The NUT is threatening industrial action if its members are expected to support assistants taking classes, if teachers are denied a reasonable work-life balance or if job losses lead to an increase in workload.
There are also fears over the implementation of the national workload agreement in Wales. With the NUT and UCAC, the Welsh-speaking teachers'
union, refusing to sign the agreement, it has the support of fewer than 50 per cent of teachers in the principality.
* The role and status of support staff was the hot topic of Education Secretary Charles Clarke's webcast for the National College for School Leadership. Several heads and school bursars posted questions about collegiality, the status of non-teaching colleagues, and how boosting staff morale.
JUST DON'T DO IT
Administrative and clerical tasks teachers will no longer have to do:
* Collecting money from pupils and parents
* Investigating a pupil's absence
* Bulk photocopying
* Typing or making word-processed versions of written material and producing revisions of them
* Word-processing, copying and distributing bulk communications, including standard letters, to parents and pupils.
* Producing lists of pupils in each class
* Keeping and filing records, including records based on data supplied by teachers
* Preparing, setting up and taking down classroom displays
* Producing analyses of attendance figures
* Producing analyses of exam results
* Collating pupil reports
* Administration of work experience (but not selecting placements and supporting pupils by advice or visits)
* Administration of public and internal examinations.
* Administration of cover for absent teachers.
* Ordering, setting up and maintaining ICT equipment and software.
* Ordering supplies and equipment.
* Cataloguing, preparing, issuing and maintaining materials and equipment or stocktaking these
* Taking verbatim notes at meetings or producing formal minutes
* Co-ordinating and submitting bids (for such things as funding,and specialist status)
* Transferring data on paper about pupils into computerised school management systems.
* Managing data in school management systems